Objective: To examine the combined influence of workplace demands and changes in blood pressure induced by stress on the progression of carotid atherosclerosis. Design: Population based follow up study of unestablished as well as traditional risk factors for carotid atherosclerosis, ischaemic heart disease, and other outcomes. Setting: Eastern Finland. Subjects: 591 men aged 42-60 who were fully employed at baseline and had complete data on the measures of carotid atherosclerosis,job demands, blood pressure reactivity, and covariates. Main outcome measures: Change in ultrasonographically assessed intima-media thickness of the right and left common carotid arteries from baseline to 4 year follow up. Results: Significant interactions between workplace demands and stress induced reactivity were observed for all measures of progression (P < 0.04). Men with large changes in systolic blood pressure (20 mmHg or greater) in anticipation of a maximal exercise test and with high job demands had 10-40% greater progression of mean (0.138 v 0.123 mm) and maximum (0.320 v 0.261 mm) intima-media thickness and plaque height (0.347 v 0.264) than men who were less reactive and had fewer job demands. Similar results were obtained after excluding men with prevalent ischaemic heart disease at baseline. Findings were strongest among men with at least 20% stenosis or non-stenotic plaque at baseline. In this subgroup reactive men with high job demands had more than 46% greater atherosclerotic progression than the others. Adjustment for atherosclerotic risk factors did not alter the results. Conclusions: Men who showed stress induced blood pressure reactivity and who reported high job demands experienced the greatest atherosclerotic progression, showing the association between dispositional risk characteristics and contextual determinants of disease and suggesting that behaviourally evoked cardiovascular reactivity may have a role in atherogenesis.